Sample retrieval device for aerosol collection

ABSTRACT

A modular aerosol sample detection system is provided comprising a sample collector couplable to an aerial vehicle and provided with at least one retrievable collection sample plate, which controllably rotates to collect aerosol samples on a multiplicity of collection spots arranged in multiple concentric tracks on the collection disk, and a multi-channel TOF removably couplable to the collection sampler to analyze the collected samples.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of prior filed U.S. ProvisionalApplication No. 60/434,614, filed on Dec. 19, 2002, the contents ofwhich are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a sample retrieval device foraerosol collection.

2. Discussion of the Related Art

Aerosol sampling has become an indispensable process used in a widerange of applications such as, for example, environmental studies,detection of airborne biological or chemical warfare agents, explorationof cosmos, etc. The collection of the impurities, especially in air, canbe realized by filtering many particles out of the air. The detection ofthe collected particles can be performed by, among others, sophisticateddiagnosing equipment, e.g., time-of-flight spectrometers.

Recently, aerosol sample retrieval for chemical analysis by massspectrometry has developed into an alternative method to on-sitemonitoring by separating a collection device from an analyticalinstrumentation. As a consequence, the use of aerosol collecting deviceshas been diversified and expanded to areas previously considered to behardly accessible.

Some of the known collecting devices operate as an impacting type deviceconfigured to force entrained particles along a path, which leads theparticles to an impactor plate, where these particles are collected uponimpact and later analyzed. One of the difficulties in using impactorscan be explained by a high kinetic energy possessed by particlesentrained in a gas stream. As a consequence, the entrained particles canbounce off the impactor plate and re-entrain the gas stream therebycausing erroneous results during a subsequent analysis. Anotherdifficulty includes a non-uniform deposit over the entire impactionplate, which is ordinarily mounted stationary mounted relative to aparticle guide. However, it is desirable that a deposit be substantiallyuniform, because it reduces particle re-entrainment.

To remedy these problems, a “virtual” impactor has been developed toseparate particulates from a fluid stream with techniques other thandirect impaction. Virtual impactors may operate on a number of differentprinciples, but all avoid actual “impact” as a means to separateparticulates from a fluid in which the particulates are entrained.Critically, virtual impactors invariably rely on differences inparticulate mass to induce inertial separation.

Still, the problems associated with actual impactors continue to persistin virtual impactors known for particle “wall loss,” i.e., unintendeddeposition of particulates on various surfaces of virtual impactorstructures, especially at curved or bent portions. As a consequence, thevirtual impactors are characterized complicated configurations,time-consuming installation and cost inefficient maintenance.

Thus, many of the known types of the actual and virtual impactors arecharacterized by a rather expensive and delicate structure difficult toinstall and maintain.

It would therefore be desirable to provide a cost-efficient,maintenance-friendly and rugged aerosol collection device, which can becoupled to a vehicle to collect aerosol samples in inaccessible orhazardous environment in a reliable manner.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a sample collector isprovided and is at least configured to be removably coupled to a vehicleand having multiple intake ports and a rotary collection plate, whichare juxtaposed with one another to provide a plurality of concentrictracks of collection spots on the sampling surface to allow forredundancy in the sample collection.

The sample collector of the present invention has been found to beparticularly advantageous when formed from lightweight materials andused with Unmanned Aerial Vehicles (UAV), e.g., radio controlledelectric powered helicopter (RC UAV), which allows for high versatility,maneuverability, and rapid interrogation of otherwise inaccessibleand/or hazardous environments. Other advantages of the UAV are its broadcommercial availability, relatively cost-efficient and simple structurecapable of carrying a payload of up to a pound. As one skilled in theart would readily appreciate, although the following discussion isdirected to RC UAV's, the sample collector of the present invention canbe associated with any type of vehicle subject only to elementarymechanical modifications of the mounting structure of the device.

In accordance with another aspect of the present invention, a samplecollector is centered along an axis of symmetry and configured so thatan air sample, traversing multiple intake ports, is branched amongmultiple outlet ports positioned asymmetrically relative to the axis ofsymmetry. The geometry of the intake and outlet ports, each pair ofwhich defines a respective air passage therebetween, can vary subjectonly to the formation of the multiple tracks of collection points on therotary plate.

In accordance with a further aspect of the present invention, thesampling surface is configured as a disk formed with a multiplicity ofconcentric arrays of ventilation holes. Each array is divided intonumerous groups each including several ventilation holes, which surrounda respective continuous region of the disk to define a collection point.Hole size affects a filtering capacity of the disk and can vary inaccordance with a given task and local requirements.

It is important to note that the manner in which samples are collectedaffects the usefulness of the samples for archival purposes. Collectedsamples are often employed to determine more information about an eventoccurring at a specific time. For example, archival data collectedduring a predetermined time and itinerary of flight might be used todetermine at what time higher levels of pollution occurred. That timecould then be applied to determine at which point of the itinerary sucha peak was detected to undertake further necessary measures depending onthe determined locale and level of detected pollutants or agents.

This feature can be addressed in accordance with a further aspect of thepresent invention by providing a method and device capable of collectingsamples for successive sampling periods, and which include time indexingenabling a specific collected sample to be correlated with a specifictime at which the sample was taken.

In accordance with another aspect of the invention, a sample collectoris an integral part of a collector/analyzer assembly configured inaccordance with the present invention. In this manner, not only can thesample collector possess the increased collecting capability, but alsoit can be readily coupled to a multi-channel time of flight (TOF) massanalyzer to provide for a time-efficient, reliable process.

The sample collector of the present invention provides for a simple andcost efficient structure configured to provide numerous samplecollections and sample identifications while being mounted to a varietyof vehicles operating in hazardous environments.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more readilyapparent from the detailed description of the invention accompanied bythe following drawings, in which:

FIG. 1 is a view illustrating the sample retrieval collection devicemounted to a radio-controlled unmanned aerial vehicle of the presentinvention;

FIG. 2 is an exploded view of the sample retrieval device of the presentinvention;

FIG. 3 is an isometric view of the sample retrieval device of thepresent invention;

FIG. 4 is a cutaway side view of the sample retrieval device of thepresent invention; and,

FIG. 5 is a plan view of a sample disk configured in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1-4, sample retrieval device 20 is configured to atleast perform numerous collections of aerosol samples in remote andhazardous areas reachable by man or remote operated vehicles.Particularly well suited as a carrier for the device 20 is a radiocontrolled (RC) battery operated helicopter 10 or an RC Unmanned AerialVehicle (RC UAV) 10, as illustrated in FIG. 1. Both highly maneuverableand easily assembleable, the RC UAV has a lightweight carbon fiber bodyincluding multiple arms 12, each of which has a rotor blade assembly 14powered by a battery set. A central control module 16 includingelectronics is mounted on the vehicle's body equidistantly from therotary blade assemblies 14 and can be configured to carry the device 20,preferably attached to the bottom of the control module. Compared toliquid operated helicopters, the RC UAV is particularly advantageous forcollecting air samples, because the latter are not compromised byotherwise contaminating fuels.

Turning specifically to FIGS. 2-4, the device 20 can be powered by itsown power source, with the batteries of the RC UAV 10 being preferred,and is characterized by a housing 50 having any suitable shape, e.g., apolygonal shape or a circular shape. In either case, the device 20 ishighly portable and designed, for example, to be about 3″ long and wideand about 3″ high.

Housing 50 of device 20 is configured to contain one or more sampleplates 52 each optionally having a disk shape, such as, for example, astandard about 3″ diameter disk mounted on a base 42 of the device. Toreliably mount the disk 52, the base 42 has an aperture 40 dimensionedto fully receive the disk 52, which is thus reliably secured in thehousing. Housed in base 42 is a motor 56 (FIG. 4) coupled to androtating the disk 52 which receives and collects a plurality of airsamples during the flight of the helicopter, as will be explained below.

To prevent interference of device 20 with the aerial maneuverability ofthe RC UAV 10, housing 50 is configured with air passages 48′ and 48″(FIG. 3) located between base 42 and top 22 of housing 50 and extendingthrough the housing to substantially reduce the air resistance of thedevice during a flight. Formation of air passages 48′ and 48″ can beobtained by an air-intake housing part 30 (FIG. 2), juxtaposed with base42, and lid 24 coupled to the upper portion of the air-intake part 30.In particular, the air-intake part 30 is shaped to have a flat lowerportion totally covering the aperture 40 and a recessed upper portionconfigured to have a pair of side flanges 34 extending from a bottom 36.The lower portion of the lid 24 carries one or more spacers 28 (FIG. 3)supported by bottom 36 and dimensioned to form the air passages 48′ and48″, each of which is defined between the spacer(s) and a respective oneof the flanges 34. The spacer(s) 28 may be variously shaped anddimensioned and is subject only to the dimensional limitations necessaryto provide air passages. Coupling top 22, lid 24, air-intake part 30 andbase 42 to one another can be realized by a plurality of fasteners (notshown) preferably extending through the corners of the of device 20.

To provide flow of air through device 20, base 42 can house a fan 58(FIG. 4) located under motor 56 and disk 52 and operative to create anegative pressure, which is sufficient to force ambient air throughmultiple intake ports 30′. The intake ports are provided in cutoutregions 32 each formed in a respective one of the flanges 34 of theair-intake part 30 (FIG. 2) of the housing 50. The configuration of theintake ports guides air samples through a plurality of passages 62leading towards disk 52, which is positioned to be impacted by the airstreams and configured to allow numerous collections during a flight.

The disk(s) 52, rotatable relative to the passages 62, areadvantageously fabricated so that two tracks of collections spots 60 and64 are arranged in concentric inner 66 and outer 68 circular tracks,respectively, as shown in FIG. 5. Arrangement of multiple concentrictracks of collection spots 60, 64 is determined by the configuration ofand position of each of the downstream ends or outlets 38 (FIG. 4) ofthe passages 62 relative to an axis of symmetry S—S (FIG. 4) of thedevice 20. Forming the downstream ends asymmetrically relative to theaxis S—S allows for as many concentric arrays as the number of intakepassages, which may be more than two depending on the arrangement of thecutout regions 32. Since the increased volume of the sample isdesirable, the outlet ports 38 are dimensioned to be larger than therest of the passages.

Preferably, the cutout regions 32 each have a triangular cross-sectionprovided with an apex 18 (FIG. 2), which is located next to a respectiveintake port 30′ (FIGS. 3 and 4), and serve as an airflow trap of airforced into these ports. Since the air passages are formed parallel, theapexes 18 are located asymmetrically to the axis S-S to form twoconcentric arrays of collections spots as shown in FIG. 2. However theparallel relationship between the passages is not critical; it is thedownstream ends of these passages that define a multi-track collectionspot arrangement on the disk 52. As a consequence, the cutout regionscan be uniform, and the intake ports can be spaced symmetrically fromthe axis of symmetry S—S, provided that the air passages extendangularly towards one another to have their downstream ends terminateasymmetrically relative to this axis. Alternatively, a micro-porousmaterial (frit or filter) may be used for the collection surface fortrapping particulates entrained in the air stream.

The motor 56 can be, for example, a stepping motor rotatably fixed tothe disk 52, which is thus indexed so that any given pair of spacedacross the sample disk 52 collection spots 60 and 64 of the inner 66 andouter 68 tracks, respectively, is always aligned with the outlet ports38. As a consequence, the multiples concentric tracks of collectionspots allow for redundancy in the sample, which, in turn, provides formore reliable detection of the collected samples.

While the sampling surface of the disk 52 is prepared using, forexample, activated charcoal, adhesives, or other sample captivatingsubstances, areas surrounding each of the collection spots 60 and 64each are drilled with an array of vent holes 70 (FIG. 5) traversed bypassing air flow. The shape, dimension and quantity of the vent holescan be selected to address the local requirements. To evacuate the airfrom the housing 50, base 42 (FIG. 3) is provided with numerous recesses72 providing flow communications between the interior of the housing andthe atmosphere.

Following the collection cycle, helicopter 10 is recovered, the sampledisk 52 is removed, and subsequently loaded into a multi-channel time offlight (TOF) mass analyzer 75 (FIG. 5), e.g., a multi-channel time offlight (TOF) mass analyzer as disclosed in U.S. Pat. No. 6,580,070 toCornish et al., the contents of which are incorporated by referenceherein. The multiple tracks are indexed through the multiple massspectrometer channels allowing for a rapid and redundant assessment ofthe environmental aerosol sample.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting the scope of the invention, but merely asexemplifications of the preferred embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

1. An aerosol sample detection system comprising: a sample collectorremovably attachable to a vehicle and comprising: a housing having aninterior; a plurality of passages formed in the housing and configuredto simultaneously provide multiple flows of aerosol sample into theinterior thereof from ambient; and, a sample plate removably mounted inthe interior of the housing downstream of the plurality of passages andhaving a sample surface, which is juxtaposed with the plurality ofpassages, the sample plate and the plurality of passages beingdisplaceable relative to one another so that multiple concentric tracksof collection spots of the aerosol sample are formed on the samplesurface upon impacting the multiple flows of the aerosol samplethereagainst; and a multi-channel time of flight (TOF) mass analyzerprovided with multiple channels and configured to receive the sampleplate, wherein when the sample plate is removed from the samplecollector and loaded into the mass analyzer, the multiple concentrictracks on the sample surface each are indexed through a respective oneof multiple channels of the TOF mass analyzer.
 2. The aerosol sampledetection system of claim 1, further comprising a pressure sourcemounted in the housing downstream from the sample plate and including afan or a pump to provide pressure differential between the interior ofthe housing and the ambient, which is sufficient to force air along theplurality of passages into the interior of the housing.
 3. The aerosolsample detection system of claim 2, wherein the housing has a modularconfiguration extending along a symmetry axis and including a baseconfigured to house the pressure source spaced axially downstream of thesample plate, an intermediary air intake part of the housing providedwith the plurality of passages and covering the sample surface, and acover topping the intermediary air intake part, wherein the base, theintermediary air intake part and the cover coextend with one another ina plane perpendicular to the symmetry axis and are detachably coupled toone another.
 4. The aerosol sample detection system of claim 3, whereinthe base of the housing is provided with multiple air outlets and has arecessed surface shaped and dimensioned to receive the sample plate. 5.The aerosol sample detection system of claim 4, wherein the intermediaryair intake part of the housing has a lower flat surface covering therecessed surface of the base and an upper surface having a flat bottomspaced from the lower flat surface and a pair of flanges spaced acrossthe flat bottom and extending axially upwards therefrom.
 6. The aerosolsample detection system of claim 5, wherein the cover abuts the pair offlanges and is provided with at least one spacer extending axiallytoward and pressing against the flat bottom, the at least one spacerbeing dimensioned to form a pair of air channels defined between the atleast one spacer and a respective one of the pair of flanges.
 7. Theaerosol sample detection system of claim 5, wherein the pair of flangeseach have a respective cutout region extending laterally inwards towardthe cutout region of the other flange and traversed by a respective oneof the plurality of passages leading into the recessed surface of thebase and terminating upstream of the sample surface of the sample plate.8. The aerosol sample detection system of claim 7, wherein the cutoutregions each have a respective substantially triangular shape and isprovided with a respective apex spaced from the symmetry axis andlocated next to an intake port, which is formed in each of the cutoutregions and is in flow communication with a respective one of theplurality of the passages traversed by the aerosol sample.
 9. Theaerosol sample detection system of claim 8, wherein the cutout regionsare non-uniformly dimensioned to have the apexes thereof spacedasymmetrically relative to the symmetry axis.
 10. The aerosol sampledetection system of claim 1, further comprising a drive mounted in thehousing and removably coupled to the sample plate rotatable so that theplurality of passages each have a respective downstream outlet portfacing the sample surface and controllably juxtaposed with thecollection spots of the multiple concentric tracks.
 11. The aerosolsample detection system of claim 10, wherein the drive is a steppermotor coupled to the sample plate.
 12. The aerosol sample detectionsystem of claim 11, wherein the sample plate is disk-shaped and isrotatably fixed to a shaft of the stepper motor.
 13. The aerosol sampledetection system of claim 11, wherein the sample surface is indexedthrough the collection spots of the concentric tracks by the steppermotor to allow numerous collections of the aerosol sample to beperformed during displacement of the sample plate and the plurality ofpassages relative to one another.
 14. The aerosol sample detectionsystem of claim 10, wherein the sample plate has a plurality of groupsof spaced apart ventilation holes, each group of ventilation holes beingarranged to surround a respective one of the collection spots of each ofthe concentric tracks on the sample surface of the sample plate.
 15. Theaerosol sample detection system of claim 1, wherein the sample surfaceincludes a substrate selected from the group consisting of charcoal oradhesives.
 16. The aerosol sample detection system of claim 1, whereinthe plurality of passages extend substantially parallel to one anotherand are spaced asymmetrically relative to a symmetry axis of the housingto provide parallel multiple flows of aerosol sample through thehousing.
 17. The aerosol sample detection system of claim 1, wherein thesample surface is made from a micro-porous material including flit orfilter configured to trap particulates entrained in the aerosol sample.18. An aerosol sample detection system comprising: a radio controlledunmanned aerial vehicle (RC UAV) having: a plurality of rotary bladeseach powered by a battery set; and a control panel spaced equidistantlyfrom the plurality of rotary blades; and, an aerosol collector removablymounted to the control panel and operative to collect multiple aerosolsamples, the aerosol collector comprising: a housing having an interiorand an axis of symmetry; a plurality of passages formed in the housingand spaced asymmetrically with respect to the axis of symmetry; a sampleplate rotatable about the axis of symmetry and removably mounted in theinterior of the housing downstream of the plurality of passages, thesample plate having a sample surface juxtaposed with the plurality ofpassages; a fan, mounted in the housing downstream from the sampleplate, that draws multiple flows of aerosol sample from ambient throughthe plurality of asymmetric passages and toward the sample surface; anda stepper motor mounted in the housing and configured to rotate thesample surface about the axis of symmetry such that the multiple flowsof aerosol sample impact the sample surface as it rotates so as to formmultiple separated concentric circular tracks of collection spotsthereon, the circular concentric tracks having (i) their respectivecenters coinciding with the axis of symmetry, and (ii) differentrespective radii.
 19. The aerosol detection system of claim 18, furthercomprising a time of flight (TOF) mass analyzer configured to receivethe sample plate and provided with multiple channels, wherein when thesample plate is removed from the sample collector and loaded into themass analyzer, the multiple concentric tracks formed on the samplesurface of the sample plate each are indexed through a respective one ofthe multiple channels of the TOF mass analyzer.
 20. A method ofdetecting an aerosol sample comprising the steps of: mounting an aerosolcollector to a radio-controlled unmanned aerial vehicle, said mountingstep comprising the further steps of: providing a housing centered alonga symmetry axis; providing a plurality of passages extending through thehousing and configured to simultaneously guide multiple flows of theaerosol sample through the housings and asymmetrically with respect tothe symmetry axis; removably placing a sample plate within the housingso that a sample surface of the sample plate opposes downstream ends ofthe plurality of passages; and, rotating the disk during a flight of theaerial vehicle about the symmetry axis and relative to the plurality ofpassages; and creating a negative pressure within the aerosol collector,wherein said negative pressure causes the multiple flows of the aerosolsample to impact the rotating sample surface so as to form multipleseparated concentric circular tracks of collection spots thereon, thecircular concentric tracks having (i) their respective centerscoinciding with the symmetry axis, and (ii) different respective radii.21. The method of claim 20, further comprising the steps of: removingthe sample plate from the housing; and, loading the sample plate into atime of flight (TOF) mass analyzer provided with multiple channels,wherein the multiple concentric tracks each are indexed through arespective one of the multiple channels of the TOF mass analyzer. 22.The method of claim 21, wherein the step of loading comprises the stepof redundantly assessing the aerosol sample collected on a group ofspaced across the sample plate collection spots of the multipleconcentric tracks.
 23. The method of claim 20, wherein the step ofrotating is provided in a time- and speed-controlled manner, therebyindexing each collection spot of the multiple concentric tracks, themethod further comprising the step of continuously powering the samplecollector during a flight of the radio-controlled unmanned aerialvehicle.
 24. An aerosol collector comprising: a housing having aninterior and an axis of symmetry; a plurality of passages formed in thehousing and spaced asymmetrically with respect to the axis of symmetry;a sample plate rotatable about the axis of symmetry and removablymounted in the interior of the housing downstream of the plurality ofpassages, the sample plate having a sample surface juxtaposed with theplurality of passages; a fan, mounted in the housing downstream from thesample plate, that draws multiple flows of aerosol sample from ambientthrough the plurality of asymmetric passages and toward the samplesurface; and a stepper motor mounted in the housing and configured torotate the sample surface about the axis of symmetry such that themultiple flows of aerosol sample impact the sample surface as it rotatesso as to form multiple separated concentric circular tracks ofcollection spots thereon, the circular concentric tracks having (i)their respective centers coinciding with the axis of symmetry, and (ii)different respective radii.
 25. The aerosol sample detection system ofclaim 10, wherein the collection spots of each of the multipleconcentric tracks are spaced uniformly from one another at a respectiveangular distance, the uniform angular distance between the collectionsspots of one of the multiple concentric tracks being different from theuniform angular distance between the collection spots of another one ofthe multiple concentric tracks.
 26. The aerosol sample detection systemof claim 10, wherein the collection spots of the multiple concentrictracks are arranged to have each of the collection spots of one of themultiple concentric tracks aligned with and spaced across the sampleplate from a respective collection spot of another one of the concentrictracks, wherein the aligned and spaced apart collections spots of theconcentric tracks are impinged simultaneously by the multiple flows ofaerosol sample exiting the outlet ports of the plurality of passages toallow for redundancy in collection of the aerosol sample on the samplesurface of the sample plate.